Photochemistry of Tricyclo[5.2.2.0 2,6 ]undeca‐4,10‐dien‐8‐ones: An Efficient General Route to Substituted Linear Triquinanes from 2‐Methoxyphenols. Total Synthesis of (±)‐Δ 9(12) ‐Capnellene

An efficient and short entry to polyfunctionalized linear triquinanes from 2‐methoxyphenols is described by utilizing the following chemistry. The Diels–Alder reactions of masked o ‐benzoquinones, derived from 2‐methoxyphenols, with cyclopentadiene afford tricyclo[5.2.2.0 2,6 ]undeca‐4,10‐dien‐8‐ones. Photochemical oxa‐di‐π‐methane (ODPM) rearrangements and 1,3‐acyl shifts of the Diels–Alder adducts are investigated. The ODPM‐rearranged products are further converted to linear triquinanes by using an O ‐stannyl ketyl fragmentation. Application of this efficient strategy to the total synthesis of (±)‐Δ 9(12) ‐capnellene was accomplished from 2‐methoxy‐4‐methylphenol in nine steps with 20 % overall yield.